Firefox stopped working

Installed the 14.8.8 codec pack & Firefox stopped working, won't connect to any website, just stays a blank page when I try

Have tried numerous websites & Chrome works just fine, so is something about Firefox that won't work with the codec pack apparently

Isn't something else causing the issues either, as Firefox stopped working IMMEDIATELY after the codec was installed

Tried restarting the laptop & Firefox still won't work

Tried uninstalling the codec pack & Firefox still won't work

How do I get Firefox to start working again?


Win 10 Pro, Firefox v66.0.2 if they matter

Uninstalled K-Lite & then went in Firefox and disable all add-ons .... restarted Firefox & enabled the add-ons again and everything is working fine

MP4s still didn't play while K-Lite was installed, so no clue what the issue is with movies playing though

Do you mean MP4 playback in Firefox? That needs/uses a specific video decoder from Microsoft.

Make sure nothing is disabled here:
Codec Tweak Tool > Media Foundation
Codec Tweak Tool > MS Codec Tweaks

If those buttons are greyed out, it means your system is missing those codecs. That is the case on European "N" versions of Windows. You can get the required stuff by installing "Media Feature Pack" from Microsoft.